Power-switching semiconductor device

ABSTRACT

In order to reduce a turn-on time of a power switching semiconductor device at a low cost, a first main electrode divided into a plurality of segments forming segment rows of a multi-concentric circle and a control electrode surrounding the segments are formed on a front major surface of a semiconductor substrate, and a second electrode is formed on a rear major surface thereof, and a turn-on operation is performed between the first main electrode and the second main electrode with a control signal inputted from the control electrode, specifying a relationship between a width of a segment and a distance between adjacent segments, and others.

This application is based on PCT international application No.PCT/JP99/03457 which has an international filing date of Jun. 29, 1999which designated the United States, the entire contents of which areincorporated by reference.

TECHNICAL FIELD

The present invention relates to improvement on a power switchingsemiconductor device such as a gate turn-off thyristor (hereinafterreferred to as “GTO”), for example, which has a first main electrodedivided into a plurality of segments and a control electrode surroundingthe segments formed on a front major surface of a semiconductorsubstrate, and a second main electrode formed on a rear major surfacethereof, respectively, and which performs a turn-on operation betweenthe first main electrode and the second main electrode with a controlsignal inputted from the control electrode.

BACKGROUND ART

A conventional power switching semiconductor device of this kind will bedescribed with reference to a schematic view of GTO shown in FIG. 4.FIG. 4 is a drawing of a semiconductor substrate viewed from a frontmajor surface thereof.

A thyristor having a self arc-extinction capability such as GTO requiresa structure endurable against a reverse bias at a turn-off, dissimilarto a common thyristor and a P base layer corresponding to a gate isformed in a mesa structure to achieve a withstand voltage of tens ofvolts. Cathode electrodes 1 (hereinafter referred to as “segments”) ofrespective small thyristors each independently fabricated in a mesastructure are arranged radially and in a concentric double ring shapeamounting to hundreds to thousands of pieces. A gate electrode 2constituting a control electrode is formed on a front major surface 3 aof a semiconductor substrate 3 in such a manner to surround the outerperiphery of the segments 1.

Note that a first main electrode 4 is constituted by connecting thesegments 1.

Further, an anode electrode 5 constituting a second main electrode isformed on a rear major surface 3 b of the semiconductor substrate 3.

The following relations was established between an inner segment row 6forming an inner concentric circle and an outer segment row 7 arrangedin a circle concentric to and outside the inner concentric circle:

0<B ₂≦α₂ ×A ₂

α₂≧1.8

(D ₂ −C ₂)/2≦β₂ ×A ₂

β₂≧1.8

where A₂ is a width of a segment in a circumferential direction, B₂ adistance between adjacent segments in a circumferential direction, C₂ anouter diameter of the inner segment row, and D₂ an inner diameter of theouter segment row.

In the GTO fabricated in such a structure, it is well known to performthe turn-on and turn-off operations, but there has been a problem that aturn-on time is long and a switching action is slow.

The present invention has been made in light of conventionalcircumstances as described above, and it is accordingly an object of thepresent invention is to provide a power switching semiconductor devicehaving a shorter turn-on time at a low cost without deteriorating theconventional characteristics.

DISCLOSURE OF THE INVENTION

The present invention is directed to a power switching semiconductordevice, in which a first main electrode divided into a plurality ofsegments forming segment rows of a multi-concentric circle and a controlelectrode surrounding the segments are formed on a front major surfaceof a semiconductor substrate, and a second main electrode is formed on arear major surface thereof, and a turn-on operation is performed betweenthe first main electrode and the second main electrode with a controlsignal inputted from the control electrode, wherein a turn-on time isreduced without adopting any special structure by specifying arelationship among the maximum width of a segment in a circumferentialdirection, the minimum distance between adjacent segments in acircumferential direction arrangement, an outer diameter of an innersegment row, and an inner diameter of an outer segment row.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a structure of a first embodiment ofthe present invention;

FIG. 2 is a graph of turn-on characteristics of the first embodiment ofthe present invention;

FIG. 3 is a graph of turn-on characteristics of the first embodiment ofthe present invention; and

FIG. 4 is a schematic view showing a structure of a conventional device.

BEST MODE FOR CARRYING OUT THE INVENTION

Detailed description will be given of the present invention based onFIGS. 1 to 3.

FIG. 1 is a schematic view showing a structure of a first embodiment ofthe present invention, and FIGS. 2 and 3 are graphs showing turn-offcharacteristics of a power switching semiconductor device of the firstembodiment of the present invention.

In FIG. 1, A₁ is a width of a segment 1 in a circumferential direction,B₁ a distance between adjacent segments 1 in a circumferential directionarrangement, C₁ an outer diameter of an inner segment row and D₁ aninner diameter of an outer segment row, and there is established thefollowing relations:

0<B _(1≦α) ₁ ×A ₁

α₁≦1.5

(D ₁ −C ₁)/2=β₁ ×A ₁

β₁≦1.5

where A₁ is a width of a segment 1 in a circumferential direction, B₁ adistance between adjacent segments 1 in a circumferential directionarrangement, C₁ an outer diameter of an inner segment row and D₁ aninner diameter of an outer segment row.

Note that reference marks other than those described above indicate thesame constituents as or corresponding constituents of those attachedwith the reference marks in FIG. 4 showing a conventional powerswitching semiconductor device, and therefore descriptions thereof areomitted.

Next, description will be given of the operations. While the performanceof the turn-on operation and turn-off operation is similar to that of aconventional device, a turn-on time “tgt” is shorter than in theconventional device, as shown in FIGS. 2 and 3.

In a constitution having such a structure like this, there can beprovided a power switching semiconductor device with reduction of aturn-on time, a faster switching speed and a less switching loss.

In addition, since the structure specifies a distance between thesegments only, a power switching semiconductor device with highperformance can be provided at a low cost due to no cost-up factorassociated with improvement on performance.

Further, while in the first embodiment, a case of GTO is shown as anexample, the present invention is not limited to GTO but can be appliedto a gate commutation thyristor (in which no snubber circuit is requiredby commutation of a main current to the gate at a turn-off) or the like.

INDUSTRIAL APPLICABILITY

As described above, a power switching semiconductor device according tothe present invention is suited for use in a power switchingsemiconductor device for controlling an inverter of a motor in anelectric locomotive and the like.

What is claimed is:
 1. A power switching semiconductor device,comprising: a first main electrode which is divided into a plurality ofsegments to form segment rows of a multiconcentric circle; a controlelectrode surrounding the plurality of segments and formed on a frontmajor surface of a semiconductor substrate; and a second main electrodeformed on a rear major surface of the semiconductor substrate, wherein aturn-on operation is performed between the first main electrode and thesecond main electrode with a control signal inputted from the controlelectrode, wherein dimensions of the power switching semiconductordevice satisfy the following relationships: 0<B≦α×A 0.5≦α≦1.5(D−C)/2≦β×A 0.5≦β≦1.5 where A is a width of each segment of theplurality of segments that form said segment rows in a circumferentialdirection, B is a distance between adjacent segments in acircumferential direction arrangement, C is an outer diameter of aninner segment row, and D is an inner diameter of an outer segment row,wherein the distance B between adjacent segments is the same for onesegment row as compared to another segment row and a distance betweenadjacent inside edges of the plurality of segments is the same for onesegment row as compared to another segment row, and wherein the width Ais the same for one segment row as compared to another segment row.